I would very much like the BLU job have a very in depth hunting log that focused more on bosses or fate monsters.
Or if we go on that idea of increased slots to cross classmore skills, maybe they unlock enhanced versions of other classes each job quest and increase tiers to allow more skills to choose from. But this sounds more like a mimic job. Perhaps if the jobs BLU and MMC? (mimic) branched from the same copycat class one delves into the complexities of other jobs/classes while the other experiments with the absurdities of monster skills. Both have the copycat skill but when the soul crystals are equipped, have different effects. BLU have copycat work like cleric stance and have reduced stats and must be attacked by the learn able skill and survive using mitigating or regenerative skills. Maybe learn a confusion or charm effect skill for a job quest to learn beneficial abilities.